VEHICLE SEAT SUSPENSION UNIT

Abstract: A damping unit (10) for a vehicle seat suspension unit has a brake slide plate (17) mounted on an anchor pin (11) on one side rail (111) of the bottom frame of the suspension unit, the anchor pin (11) being received in a non-circular hole provided with an O-ring (15). A transfer assembly (115) has a pivot pin (19) received in an elongate slot (21) in the brake slide plate (17), and brake washers (22), compressed by Belleville washers (24), are clamped between brackets (127) on the transfer assembly (115) and the brake slide plate (17). On small displacement from a preset datum, the brake slide plate (17) moves relative to the anchor pin (11) and no damping force is generated. When a preset displacement is exceeded, the anchor pin (11) restrains the brake slide plate (17) and the pivot pin (19) moves in the slot (21) to generate a constant damping force between the brake slide plate (17) and brake washers (22).

Description: TITLE: "VEHICLE SEAT SUSPENSION UNIT" BACKGROUND OF THE INVENTION 1. Field of the Invention THIS INVENTION relates to a vehicle seat suspension unit. In particular, it relates to a "deceleratσr" or damper for such a suspension unit. 2. Prior Art In International Application Noε. PCT/AU90/00144 (WO 90/11841) and PCT/AU92/00647 (WO 93/10996), we disclosed vehicle seat suspension units where a single transfer assembly transfers the spring force to the seat platform at a varying rate. SUMMARY OF THE PRESENT INVENTION It is an object to provide a damping means where there is substantially zero damping about an initial preset seat height but where the damping increases as the deflection of the seat from the preset height increases. It is a preferred object to provide a unit which allows an overall reduction in spring rate which in turn provides an increase in isolation efficiency. Other preferred objects will become apparent from the following description. Throughout the specification, a vehicle seat suspension unit "of the type defined" shall be used to include a suspension unit having: a base frame mountable on a vehicle; a seat support frame to mount an operator's seat; a scissor arms assembly interconnecting the frames to enable the frames to move relative to each other substantially in parallelism; a transfer assembly pivotally mounted on one of the frames, having at least one arm engaging the other of the frames; and spring means mounted on the one frame and connected to the transfer assembly. In one aspect, the present invention resides in a "deceleration" or damping unit for a vehicle seat suspension unit (eg. of the type defined) including: a brake slide plate having a longitudinal slot at or adjacent one end thereof and a hole at or adjacent the other end; an anchor pin passing through the hole and mounted on one frame of the vehicle seat suspension unit; resilient ring or washer means about the anchor pin received within the hole to allow at least limited movement of the brake slide plate relative to the anchor pin; a pivot pin on a transfer assembly of the vehicle seat suspension unit passing through the slot and arranged for movement within the slot substantially parallel to the longitudinal axis of the brake slide plate; at least one brake disc or washer interposed between the transfer assembly and the brake slide plate; and means to apply a clamping or frictional load between the brake disc or washer and the brake slide plate; so arranged that when the vehicle seat suspension unit is displaced in an initial small distance from a preset position, the brake slide plate moves relative to the anchor pin to provide substantially zero damping, but on further displacement, the brake slide plate is moved relatively to the pivot pin and a substantially constant damping force is generated between the brake slide plate and the brake disc or washer. Preferably, the damping force is substantially constant throughout the full range of displacement from the initial small distance. Preferably, the damping force may be selectively set by varying the damping force applied between the brake slide plate and the brake disc(s) or washer(s) . Belleville springs or compression washers may be provided on the pivot pin to transfer the damping force from an adjustable nut on the pivot pin to the brake slide plate and brake disc(s) or washer(s). Preferably, the hole is slightly eccentric, being preferably non-circular and formed by two circles with spaced centres. Preferably, when the vehicle seat suspension unit is displaced, the initial small distance, the brake slide plate and pivot pin move in unison but on further displacement, the brake slide plate engages and is restrained from further movement by the anchor pin and the brake slide plate moves relative to the pivot pin. In a second aspect, the present invention resides in a vehicle seat suspension unit of the type defined fitted with the "decelerator" or damping unit. BRIEF DESCRIPTION OF THE DRAWINGS To enable the invention to be fully understood, a preferred embodiment will now be described with reference to the accompanying drawings, in which: FIGS 1 and 2 are side views of the vehicle seat suspension unit in its raised and lowered positions, respectively; FIGS 3 and 4 are sectional side views of the unit corresponding to FIGS 1 and 2, respectively, with parts omitted for clarity; FIG 5 is a front view of the transfer assembly, with one of the springs and one damping unit shown in dashed lines; FIG 6 is a side view corresponding to FIG 5; FIG 7 is a side view of the brake plate when assembled; and FIG 8 is a sectional top view of the damping unit when installed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The vehicle seat suspension unit 100 has a bottom frame 110 (with side rails 111) and a top frame 112 (with plate 113) interconnected by a scissor arms assembly 114 for relative movement substantially in parallelism (ie. see WO 90/11841) and WO 93/10996). The bottom frame 110 is bolted to the seat slides, fixed to the vehicle floor, and the operator's seat is secured to the top frame 112 (see in particular WO 93/10996). A transfer assembly 115 has a tubular body 116 journalled on an axle 116a interconnecting brackets 117 on the side rails 111 of the bottom frame 110. A pair of transfer arms 118 extend from the body 116 and support the axle 119 for rollers 120 which bear on the underside of the plate 113 on the top frame 112. Two springs 121, anchored at one end to the bottom frame 110, are connected to respective pairs of brackets 122 extending below the tubular body 116 of the transfer assembly 115. By selective adjustment of the anchoring of the coil springs 121 (eg. by an electrically driven adjustment unit 123), the suspension unit 100 can be preset to a given ride height for the seat which sets a datum. A respective pair of links 124 are pivotally connected to the side rails 111 of the bottom frame 110 and have pins 125 slidable in slots 126 in the side rails 127 of the top frame 112. The links 124 limit the forward displacement of the top frame 112 relative to the bottom frame 110 if the vehicle should be involved in an accident and so the links 124 assist in securing the seat from breaking away from the vehicle. The damping unit 10 will now be described. A respective anchor pin 11 passes through each side rail 111 of the bottom frame 110 and through a boss 12 on a bracket 117. The anchor pin 11 is fitted with a nut 14. The pin 11 passes through an O-ring 15 (see FIG 7) in an elongate hole 16 in a planar brake slide plate 17. (The hole 16 is formed by two circles with offset centres and allows limited movement of the brake slide plate 17 relative to the anchor pin 11 along the longitudinal axis of the brake slide plate 17. ) (Washers 18 may be provided to allow low friction movement of the brake plate 17 between the boss 12 and the lower end of the inner scissor arms 124 of the scissor assembly 114. ) The lower ends of the inner scissor arms 124 are slotted, with the anchor pins 11 passing through the slots 125 and the arms 124 are supported for low friction on the anchor pins 11 by bearings 126. A respective pivot pin 19, with head 20, is supported by a respective pair of brackets 127 at each end of the tubular body 16 and pass through an elongate slot 21 along the longitudinal axis of the brake slide plate 17. A pair of fibre brake washers 22 are interposed between the brake slide plate 17 and brackets 127 and a damping force thereon is provided by a nut 23 and a pair of Belleville spring washers 24. As the brake slide plate 17 moves relative to the pivot pin 19 and the fibre brake washers 22 a constant friction is generated between the brake plate 117 and the brake washers 22. At the datum height of the seat, the anchor pin 11 is intermediate the hole 16 in the brake slide plate 17 (see FIG 7). For small initial displacements of the suspension unit 100, the brake slide plate 17 will move relative to the anchor pin 11 without the latter engaging a side of the hole 16. (The O-ring compression softens any initial impact when the anchor pin 11 engages either side of the hole 16.) There is no movement of the brake slide plate 17 relative to the pivot pin 19 as the brake slide plate 17 moves in unison with brackets 127 on the transfer assembly 115. If the displacement of the suspension unit 100 causes the brake slide plate 17 to engage the anchor pin 11 on one side of the hole 16, then further displacement causes the anchor pin 11 to restrain the brake slide plate 17 and thereby pull (or push) the brake slide plate 17 relative to the brackets 31 on the transfer assembly, and also relative to the brake washers 22. The constant rate friction generated between the brake slide plate 17 and brake washers 22 creates a decelerating or damping force to oppose the displacement and this damping force will also be generated as the suspension unit returns to (or passes) the datum position. (On the return stroke, the brake slide plate 17 will move so that the anchor pin 11 will engage the opposite side of the hole 16.) It will be readily apparent to the skilled addressee that the decelerator or damping unit 10 provides substantially z.ero damping about the datum (ie. zero displacement) position of the suspension unit 100 but will provide substantially constant damping once a preset displacement is exceeded. This enables very high isolation of the seat from the vehicle to be achieved, whilst having only a very low spring rate in the springs 121. Various changes and modifications may be made to the embodiments described and illustrated without departing from the scope of the present invention defined in the appended claims.

Claims: CLAIMS: 1. A "deceleration" or damping unit for a vehicle seat suspension unit including: a brake slide plate having a longitudinal slot at or adjacent one end thereof and a hole at or adjacent the other end; an anchor pin passing through the hole and mounted on one frame of the vehicle seat suspension unit; resilient ring or washer means about the anchor pin received within the hole to allow at least limited movement of the brake slide plate relative to the anchor pin; a pivot pin on a transfer assembly of the vehicle seat suspension unit passing through the slot and arranged for movement within the slot substantially parallel to the longitudinal axis of the brake slide plate; at least one brake disc or washer interposed between the transfer assembly and the brake slide plate; and means to apply a clamping or frictiαnal load between the brake disc or washer and the brake slide plate; so arranged that when the vehicle seat suspension unit is displaced an initial small distance from a preset position, the brake slide plate moves relative to the anchor pin to provide substantially zero damping, but on further displacement, the brake slide plate is moved relative to the pivot pin and a substantially constant damping force is generated between the brake slide plate and the brake disc or washer. 2. A damping unit according to Claim 1 or Claim 2 wherein: the damping force is substantially constant through the full range of displacement from the initial small distance. 3. A damping unit according to Claim 1 or Claim 2 wherein: the damping force may be selectively set by varying the damping force applied between the brake slide plate and the brake disc(s) or washer(s). 4. A damping unit according to Claim 3 wherein: Belleville springs or like compression means are provided on the pivot pin to transfer the damping force from an adjustable nut on the pivot pin to the brake slide plate and the brake disc(s) or washer(s). 5. A damping unit according to any one of Claims 1 to 4 wherein: the hole is slightly eccentric, being non- circular and formed by two circles with spaced centres. 6. A damping unit according to any one of Claims 1 to 5 wherein: when the vehicle seat suspension unit is displaced the initial small distance, the brake slide plate and pivot pin move in unison but on further displacement, the brake slide plate engages and is restrained from further movement by the anchor pin and the brake slide plate moves relative to the pivot pin to generate the damping force. 7. A damping unit as claimed in Claim 6 wherein: the limited movement of the brake slide plate relative to the anchor pin is substantially parallel to the longitudinal arm of the brake slide plate. 8. A vehicle seat suspension unit including: a base frame mountable on a vehicle; a seat support frame to mount an operator's seat; a scissor arms assembly incorporating the frames to enable the frames to move relative to each other substantially in parallelism; a transfer assembly pivota 1y mounted on one of the frames, having at least one arm engaging the other of the frames; spring means mounted on the one frame and connected to the transfer assembly; and a decelerator or damping unit including: a brake slide plate having a longitudinal slot at or adjacent one end thereof and a non-circular hole at or adjacent the other end; an anchor pin passing through the hole and mounted on one of the frames; resilient ring or washer means about the anchor pin received within the hole to allow at least limited movement of the brake slide plate relative to the anchor pin; a pivot pin on the transfer assembly passing through the slot and arranged for movement within the slot substantially parallel to the longitu in l axis of the brake slide plate; at least one brake disc or washer interposed between the transfer assembly and the brake slide plate; and means to apply a clamping or frictional load between the brake disc or washer and the brake slide plate; so arranged that when the vehicle seat suspension unit is displaced an initial small distance from a preset position, the brake slide plate moves relative to the anchor pin to provide substantially zero damping, but on further displacement, the brake slide plate is moved relative to the pivot pin and substantially constant damping force is generated between the brake plate and the brake disc or washer. 9. A vehicle seat suspension unit according to Claim 8 wherein: the damping force is substantially constant through the full range of displacement from the initial small distance. 10. A vehicle seat suspension unit according to Claim 8 or Claim 9 wherein: the damping force may be selectively set by varying the damping force applied between the brake slide plate and the brake disc(s) or washer(s). 11. A vehicle seat suspension unit according to Claim 10 wherein: Belleville springs or like compression means are provided on the pivot pin to transfer the damping force from an adjustable nut on the pivot pin to the brake slide plate and the brake disc(s) or washer(s). 12. A vehicle seat suspension unit according to any one of Claims 8 to 11 wherein: the hole is slightly eccentric, being non- circular and formed by two circles with spaced centres. 13. A vehicle seat suspension unit according to any one of Claims 8 to 12 wherein: when the vehicle seat suspension unit is displaced the initial small distance, the brake slide plate and pivot pin move in unison but on further displacement, the brake slide plate engages and is restrained from further movement by the anchor pin and the brake slide plate moves relative to the pivot pin to generate the damping force. 14. A vehicle seat suspension unit according to Claim 13 wherein: the limited movement of the brake slide plate relative to the anchor pin is substantially parallel to the longitudinal axis of the brake slide plate.

Inventors: CULLEY DONALD M JR, CULLEY, DONALD, MAXWELL, JR.
Applicants: CULLEY DONALD MAXWELL JR, ROSDON ENG & MFG, CULLEY, DONALD, MAXWELL, JR., ROSDON ENGINEERING & MANUFACTURING PTY. LTD.
Application year: 1994
Main classification: B60N2
IPC codes: B60N2